The present invention concerns brackets for attaching an electrical cable to a vehicle. More particularly, but not exclusively, this invention concerns a bracket for attaching to a fuel tank of an aircraft in order to secure an electrical cable. The invention also concerns an electrical assembly comprising a plurality of such brackets, a fuel tank comprising a plurality of such brackets, an aircraft comprising a plurality of such brackets or such an electrical assembly or fuel tank and a method of attaching a cable to a vehicle.
Such brackets are often used to securely hold electrical cable, which is part of a Fuel Quantity Indication (FQI) System of an aircraft. The cable has to be held within the aircraft fuel tank, generally contained within the wing of an aircraft. To comply with the electrical installation requirements, any cable must be maintained at a minimum gap of 10 mm from the fuel tank structure. The cable must have a greater clearance from other systems. It also must remain firmly in position with the minimum possible amount of sag between brackets for the life of the aircraft.
In a metallic fuel tank (for example, made out of aluminium alloy), the brackets are nylon coated aluminium and are attached to stringers and ribs of the fuel tank by drilling and riveting. Two nylon cable-ties are then used at each point of contact along the stringers/ribs to prevent the cable moving.
In a composite wing box, the brackets must be made from a fully insulating material and metal rivets cannot be used to attach the bracket to the fuel tank. Therefore, for composite wings, the brackets used are made from a composite, insulating material, such as PEI (Polyetherimide) or glass fibre re-enforced plastic. The brackets are attached to the fuel tank by adhesive bonding. The nylon cable-ties are tightened using a torque gun (not shown) set at an appropriate torque for the cable-tie being used.
Such a bracket, with the cable and cable-tie in place, is shown in FIGS. 1a and 1b. The bracket 1 has a flat bonding face 2 at one end for attaching to a stringer 3 of the fuel tank. At the opposite end, the bracket has a generally flat and square shaped cable mounting face 4. On each corner of the mounting face 4 is a locating bump 8. These locating bumps 8 provide abutment surfaces for the cable 6 to rest on or against, thereby ensuring the cable rests in a certain position on the bracket 1. On each side of the square face, is a slot 5 for a cable-tie. The cable 6 is secured to the cable mounting face 4 by a cable-tie 7 looped around the cable 6 and cable mounting face 4 through two opposite cable-tie slots 5.
FIG. 2 shows part of a wing box layout, showing the position of the brackets and cable 6, in relation to the stringers 3 and ribs 9 of the fuel tank. The cable 6 is generally run along the length of the stringers 3 and is attached to the stringers at various points with a single bracket 1. These points are approximately 150 to 200 mm apart. The spacing of the points is decided based on maintaining a minimum clearance distance even in the event of a cable-tie/bracket failure, and the resulting “skipping rope” effect of the cable between the brackets either side of the failure being able to swing. When the cable crosses over/under a stringer 3 or a rib 9, two brackets 1 are used, one either side of the stringer/rib.
However, as time passes, the cable becomes loose in the cable-tie and moves about in the bracket. This means the cable can swing in each bracket, decreasing the distance from the cable to the stringers/ribs of the fuel tank.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved bracket.